package com.base.jvm;

import java.util.*;

/**
 * create by yongli on 2021-03-26 11:49
 */

public class NullTest {
    public static void main(String[] args) {
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("ddd","");
        String str = (String)map.get("ddd");
        System.out.println(str);
        // "2000" > "1000"
        System.out.println("100".compareTo("1000"));
        System.out.println("31".compareTo("123"));

        LinkedList<Integer> ls = null;
        // 值复制
        LinkedList<Integer> ls2 = ls;
        ls = new LinkedList<>();
        ls.add(99);
        System.out.println(ls2);
    }
}
